This document relates to wireless communications in wireless communication systems.
As used herein, the terms “user equipment” and “UE” can refer to wireless devices such as mobile telephones, personal digital assistants (PDAs), handheld or laptop computers, and similar devices or other User Agents (“UA”) that have telecommunications capabilities. In some embodiments, a UE may refer to a mobile, wireless device. The term “UE” may also refer to devices that have similar capabilities but that are not generally transportable, such as desktop computers, set-top boxes, or network nodes.
In traditional wireless telecommunications systems, transmission equipment in a base station or other network node transmits signals throughout a geographical region known as a cell. As technology has evolved, more advanced equipment has been introduced that can provide services that were not possible previously. This advanced equipment might include, for example, an evolved universal terrestrial radio access network (E-UTRAN) node B (eNB) rather than a base station or other systems and devices that are more highly evolved than the equivalent equipment in a traditional wireless telecommunications system. Such advanced or next generation equipment may be referred to herein as long-term evolution (LTE) equipment, and a packet-based network that uses such equipment can be referred to as an evolved packet system (EPS). Additional improvements to LTE systems and equipment result in an LTE advanced (LTE-A) system. As used herein, the phrase “base station” will refer to any component or network node, such as a traditional base station or an LTE or LTE-A base station (including eNBs), that can provide a UE with access to other components in a telecommunications system.
In mobile communication systems such as E-UTRAN, a base station provides radio access to one or more UEs. The base station comprises a packet scheduler for dynamically scheduling downlink traffic data packet transmissions and allocating uplink traffic data packet transmission resources among all the UEs communicating with the base station. The functions of the scheduler include, among others, dividing the available air interface capacity between UEs, deciding the transport channel to be used for each UE's packet data transmissions, and monitoring packet allocation and system load. To facilitate communications, a plurality of different communication channels may be established between a base station and a UE. The scheduler dynamically allocates resources for Physical Downlink Shared CHannel (PDSCH) and Physical Uplink Shared CHannel (PUSCH) data transmissions, and sends scheduling information to the UEs through a Physical Downlink Control CHannel (PDCCH).
As the label implies, the PDCCH is a downlink channel that allows the base station to control a UE during data communications. To this end, the PDCCH is used to transmit control information within control data packets referred to as Downlink Control Information (DCI) messages. The control information conveyed within DCI messages may be used to transmit uplink or downlink scheduling assignments (for PUSCH and PDSCH respectively) or to convey other control information. The control information may be directed towards or addressed to one UE, a group of UEs, or all UEs within the cell. Downlink scheduling assignments may be sent to a UE to indicate to the UE parameters related to the formatting of a forthcoming transmission of downlink communication traffic packets by the base station on a Physical Downlink Shared Channel (PDSCH) and to indicate the location of the physical resources to be used for that transmission. Uplink scheduling assignments may be sent to a UE to indicate parameters related to a forthcoming transmission of uplink communication traffic packets by the UE on a Physical Uplink Shared Channel (PUSCH) and to indicate the location of the physical resources on which the transmission may take place. DCI messages may also convey other types of control information or provide specific instructions to the UE (e.g., power control commands, an order to perform a random access procedure, or a semi-persistent scheduling activation or deactivation). A separate DCI packet may be transmitted by the base station to a UE for each traffic packet/sub-frame transmission.